Memory devices are typically provided as internal, semiconductor, integrated circuits in computers or other electronic devices. There are many different types of memory including random-access memory (RAM), read only memory (ROM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), and flash memory.
Flash memory devices have developed into a popular source of non-volatile memory for a wide range of electronic applications. Flash memory devices typically use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption. Common uses for flash memory include personal computers, personal digital assistants (PDAs), digital cameras, and cellular telephones. Program code and system data such as a basic input/output system (BIOS) are typically stored in flash memory devices for use in personal computer systems.
Flash memory devices can have a areas of memory that are one time programmable (OTP) memory blocks. For example, in a NOR-type flash memory device, the OTP area could be the mini-array that is used by the manufacturer to store data such as the locations of redundant columns, lock bits for specific memory blocks, or other data used by the device's controller.
These mini-arrays, however, take up valuable real estate on the memory die that can be used for the main memory array. This results in an additional cost to the chip manufacturer when the manufacturer is already selling the devices at a small profit margin in order to remain competitive.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a flash memory that has one time programmable memory that does not require additional lock circuitry.